The prevention of unauthorized entry of vehicles to a facility has increased in importance in the recent past. Typically, a vehicle barricade is disposed across a roadway in order to control entry or exiting into or from a restricted facility. These barricades normally have a barrier plate which is pivotal between a first lowered position, permitting passage along the roadway, and a second raised position, preventing such passage. A hydraulic cylinder and piston assembly or other mechanical mechanism is normally employed to pivot the barrier plate between the non-operative lowered position and the operative raised position.
The inventor has developed several of these barricades; however, there are drawbacks to these security systems. In particular, U.S. Pat. Nos. 4,826,349 and 4,850,737 disclose an underground vehicle barricade having a barrier plate pivotally associated with frame means for being pivoted between a first position overlying the frame means and a second position disposed angularly upwardly relative to the frame means. Since the hydraulic operating mechanisms are located within the frame means, a rather large excavation is required to install such a vehicle barricade. Further, the hydraulic operating system is complex as a number of pivotal links are required.
Aboveground vehicle barricades are known as discussed in U.S. Pat. No. 4,850,737; but, elaborate support structures are required to absorb the impact forces caused by vehicle collisions with the barrier plate as shown in U.S. Pat. Nos. 4,574,523 and 4,630,395. Moreover, these known barricades tend to buckle when an oncoming vehicle crashes into the raised barrier plate.
Further, the hydraulically operated systems associated with the prior art employ either a single cylinder and piston assembly or a dual assembly system. Since conventional barrier plates are extremely large and thick in size, several thousand pounds of hydraulic pressure are necessary to pivotally move the barrier plate which can weight several thousand pounds. Since such high operating pressures are not desirable due to safety concerns and the added expense of special pumps or motors necessary to operate the hydraulic system, vehicle barricades have been constructed with a parallel, dual hydraulic system or a counterweight has been secured to a gate plate extending from the barrier plate to lessen the operating pressure of each hydraulic cylinder. However, the hydraulic operating pressure must be of a level sufficient to withstand the impact of a speeding vehicle. Thus, the reduction of hydraulic pressure has been limited.
Therefore, it can be seen that there is a need for a vehicle barricade or barrier which has a pivotal gate which is manufactured from a heavy gauge steel or other metal so that its mass is sufficient to withstand the impact of a speeding vehicle. Moreover, the vehicle barrier should be constructed so that the heavy gauge barrier gate can be moved between a non-operative position and an operative position with a minimum of effort. Likewise, the operating mechanisms should be simple and inexpensive to maintain but provide rapid pivoting of the barrier plate so that unauthorized vehicles can be stopped within a minimal amount of time.